Dealkylation process



Patented Nov. 26, 1940 UNITED STATES PATENT OFFICE 2,222,632DEALKYLATION PROCESS Alexander N. Sachanen and Rowland 0. Hansford,Woodbury, N. 1.,assignors to Socony- Vacuum Oil Company, Incorporated,New York, N. -Y., a corporation or New York No Drawing.

Application October 8, 1938,

Serial No. 234,012

14 Claims.

terial for motor fuels, due to the high anti-knock qualities of theallgyl aromatic compounds. This latter use of alkylated aromaticcompounds is 15 especially important for motor fuels of high compressiontype engines as, for example, the engines designed for aviation. Sincethe alkylated benzenes must be of the 'gasoline boiling range in orderto be blended with the motor iuels, various processes have been proposedto produce high yields of alkyl aromatic compounds which are within thedesired boiling range.

For the most part prior processes of preparing particular alkyl aromaticcompounds partake of chemical synthesis reactions in which aromaticcompounds such as benzene are condensed with appropriate aliphaticcompounds. It has also been proposed in the past to reform polyalkylaromatic compounds as, for instance, natural 00- curring aligylaromatics of coal tar, such as imlene, or by reforming polyalkylaromatic products produced during alkylating processes, such as notedabove. These prior processes of reiorini-ng polyalkyl aromatic compoundshave been carried out either at relatively low temperatures as, forinstance, temperatures below about 300 F. and in the presence ofcatalysts, such as aluminum chloride or sulfuric acid, or the processeshave involved merely a cracking operation at high temperatures in theabsence of catalysts. While it is true these prior processes havebrought about dealkylation of polyalkylated aromatlcs to a certainextent, they are subject to many disadvantages.

45. The most serious objection to dealkylatlon processes at lowtemperaturesin the presence of catalysts, such as aluminum chloride isthat it is a very slow process which lasts many hours or days in orderto form a substantial yield of 5 low boiling aromatics. While vtheinordinate amount of time required for such low temperature processes isthe most serious disadvantage, another objection to their use is that oflow yield of low boiling point aromatic compounds and especlally whentreating alkyl aromatics containing relatively long chain aliphaticradicals. Moreover, increases of temperature in this dealkylationprocess result in the formation of sludge and tarry materials. Thesecatalytic processes conducted at low temperatures are also open to otherobjections. For instance, such processes when employing the usual lowtemperature-reactive catalysts, such as aluminum chloride and sulfuricacid consume a relatively high quantity of catalytic material or, if thecatalyst is not entire- 1 ly consumed, a complicated and costly processof regeneration is required. Moreover, many of these catalytic materialsare corrosive to the materials of construction normally used andintroduce this as well as other operating difiiculties. 15

The most serious objection to the prior processes which involve anon-catalytic cracking operation is that of low yield of low boilingaromatics. However, in addition to this disadvantage, this type ofprocess also forms a consider- 20 able amount of heavy residua of thenature of coke and asphaltic material.

It is an object of this invention to produce 7 an emclent process foreffecting the dealkylation of monoand polyalkyl cyclic compounds to pro-25 duce aromatic compounds of lower boiling point.

A more specific object of this invention is to provide an efficientprocess for efiecting the dealkylation of monoand polyalkylated aromaticcompounds of relatively high boiling point to produce substantial yieldsof alkyl aromatic compounds of motor fuel boiling point.

Another object of this invention is to provide an efiicient process forefl'ecting the dealkylation of monoand polyalkylated compounds ofrelatively high boiling point to produce substantial yields of alkylaromatic compounds of lower boiling point and which may be carried outin a relatively short time as compared to prior catalytic processesafforded by the prior art. 40

Our invention is based upon the discovery that .alkyl cyclic compoundsmay be treated with benular weight alkyl benzenes, the destructivedealkylation by benzene may be according to the general equation whereinthe alkyl radical R is broken down into smaller radicals R1 and Ba:

The amount of benzene that may be used may vary considerably. From apractical standpoint we have found a ratio of benzene to materialtreated of about /2 volume to 2 volumes of benzene to 1 volume ofmaterial treated usually gives proper proportioning for obtaining ourdesired results. It is to be understood, however, the invention is notlimited to the above ratio but rather contemplates the broad use ofbenzene in any amount which gives our novel results.

In addition to treating with benzene, we have carried out thedestructive dealkylation of alkyl cyclic compounds by treating withother aromatic hydrocarbons instead of benzene, for example,naphthalene, alpha methyl naphthalene and alkyl na-phthalenes. Theyields of low boiling alkylated benzenes in these experiments are muchlower than with benzene. This indicates that the capacity of naphthalenefor alkylation is much less than that of benzene at these temperatureswhich might be expected, due to the relatively higher thermal stabilityof alkylated benzenes.

The alkyl cyclic compounds which may be treated in accordance withourprocess include not only monoand poly-alkylated benzenes, but alsomonoand poly-alkylated naphthalenes and other poly-cyclic alkyl aromaticcompounds as well as various monoand poly-cyclic alkylated naphthenes.While these compounds may be obtained from any suitable supply, aconvenient source that might be mentioned by way of example is theheavier portion of the product of an alkylation process for alkylatingaromatic material wherein the heavier portion comprises aromaticmaterial which has been alkylated beyond the desired degree.

Thus these alkyl aromatic hydrocarbons boiling for example, above400-435 F. are easily transformed into lower molecular weight aromaticsboiling up to 400 F. or only 300 F. by destructive dealkylation underthe conditions of our process, giving a yield of lower boiling aromaticswhich is much higher than that produced by the known processes of lowtemperature dealkylation or the usual cracking process.

The catalysts with which this invention is concerned are those which arecommonly known as clay type. In addition to the various clays themselvesand the various activated clays, there are numerous other porousrefractory adsorptive materials of similar nature and of neutralcharacter which may be used and come under-the common designation ofclay-type catalysts, for example, fullers earth, putnice and granulardiatomaceous earth. Furthermore, it is to be understood that thesevarious clay type catalysts which have other suitable catalytic materialimpregnated therein or thereon or otherwise conjoined for service mayalso be used.

.Since the dealkylation reaction together with the attendant crackingreactions which are present at the temperature herein disclosed bringabout a gradual poisoning or deterioration of the catalyst by thedeposition of carbon and carbonaceous impurities thereon, it is well touse a clay which is possessed of suflic-ient refractory nature so thatit may be regenerated in situ by burning. In fact, some of the claycatalysts used by us have been regenerated a great number of times andare still quite satisfactory. Because of the ease with which the claytype catalyst may be regenerated, they afford a substantial advantage intheir use. It is also well to use clay particles of such physical naturewith respect to size and dimension that they may be effectively packedtogether in a catalytic mass and yet, at the same time, present asuflicient cross-sectional area of flow that the reactants may have aready passage therethrough, as well as a suitable exposure of catalyticmaterial to reactants. A convenient and efiicient form for the catalystis small granules, rods or cylinders.

The use of clay catalyst has many distinct advantages in addition tothose already named. For instance, the clay is not corrosive to thenormal apparatus as are many catalysts and, furthermore, there isrelatively small consumption of the catalyst during operation. However,the most important advantage in the use of clay type catalyst is thatunder operable conditions there is obtained such markedly improvedresults asto increase yield and decrease time of operation.

The temperature employed in our process should be upwards of about 800F. It is desirable to maintain the temperature between about 800 andabout 900 F. unless the process is to be operated in a continuous mannerwhen temperatures up to about 1050 F. may be used.

While the process should be carried out under super-atmosphericpressures in batch operation, there is a wide range in the pressuresthat may be used. In the preferred embodiment of our invention for batchoperation, we employ pressures between about 1000 and 2500 pounds persquare inch. It is to be understood the process may be carried out atother pressures as, for instance, in

, continuous operation the pressure might be much lower than 1000 poundsper square inch, in fact for continuous operation atmospheric pressureor pressures of only a few atmospheres are preferred. As a whole, theoperations at these different pressures give very close results relativeto the yields and properties of products, recovery of benzene etc.

Under the conditions of our process the destructive dealkylation usuallytakes place in about fortyminutes for batch operation at 900 F., forexample, which represents a remarkable improvement over prior processeswhich require far greater lengths of time and do not give the highyields of low boiling aromatic compounds produced by our process. tionat 1000 F., for example, the time of reaction is usually around oneminute,

In order to further point out the differences between our process andthe processes of low temperature catalytic reactions heretofore enjoyedby the art, we may discuss the reactions involved. For example, whendi-amyl benzene is deal- In continuous opera Thus, according to thisprocess, as may be obthe pressure was 2200 lbs./sq. in. Otherwise the 5served, di-amyl benzene is converted into two conditions of the twoprocesses were the same, molecipzs of amyl benzene which has a boilingi. e., the temperature was 900 F. and the reaction point of 401 R, whichis barely within the upper time was 40 minutes. The following resultswere limits acceptable for ordinary motor fuel and obtained from thesetwo processes:

which is unacceptable for use in lighter gasolines 10 as, for example,aviation gasoline. 0mm Catalytic In contrast to the above reaction, thereactions I g dialkyhmn of our process when treating the same di-amylbenzene are of the following nature. g iffiigiggrgggj m y 868 l 15 (1)C6H4-(C5Hll)2+C5H6 2C6H5-C5H11" g gg g g "'7 z; A's H and, for Instance,Rt 3;t%...::::::::::: igfiiififsiififi: zit-12035515? 2)2C6H5.C5H11=2CsH5.C2H5l-2C3H6 ggg fi ggifff ff 5% New and similarequations for the formation of other Total 100% 116%- alkyl benzenes. Ifthe process is carried out 29 under high pressure, secondary reactionsof al- It is to be noted that by our process there was kylation arepossible, as, for instance, produced 62% of dealkylated aromatic boilingin the desired range of 95.to 150 C., while only (3)2C3H6+2C6H6=2C6H5C3H7 of such compounds were produced by the 25Accordingly, in our process the final products obcracking process.Moreover, the cracking proc-. 25 tained are low boiling alkyl benzeneswhich may e produced 5% of carbon. and insoluble asbe d even in the l wboiling y s of gasoline. phaltic material whereas our process producedsuch as aviation gasoline. These differences in none, 1 is also t b t dthatthe total amount the type of reaction encountered are even more of,11 rec vered products in our catalytic de- 30 striking when thealiphatic radicals of the alkyl alkylation process was 116%. In otherwords, 30 aromatic compounds have a greater number of 3% of th benzenecharged was consumed in the carbon atoms. However it is not only thefinal process of dea1ky1ati0n.' product that establishes a strikingdifierence over F rthe tests were carried out comm-ri gthe prlor wp turetalyt c p sses. ut. present process with that'of cracking and alsofurthermore, the Very substantial decrease in recrackingnin the presenceof clay without benzene 35, 7

action time is of particular importance, especiala d cracking inthepresnce of benzene without 3' m a Practical standpoint clay. In theseexperiments alkylated aromatic It is also to be noted that thedestructive dehydrocarbons boiling in the range of 150 alkylation ofalkyl benzenes to benzene progresses t 2509.6, (obtained by alkylatingbenzene with 40 more and more with increasing reaction time. olefines)were employed as a material for the de- 40 Accordingly, by suitablyextending the time of structive dealkylation. The destructivedealkylareaction more than 100% benzene (based on the tion was carriedout at a temperature of 900 amount of benzene charged to the reaction)may F. (482 C.) under a pressure of about 1,000 be recovered from thefinal products due to 9- pounds per square inch for a time of 40minutes.

Complete dealkylation 0f P t Of the alkyl The relative amount of benzeneused was two vol- 45 aromatics. In other words, under the dealkylatumesper one volume of material to be alkylated. ing action of clay, alkylbenzenes may be com- These experiments gave the following results:

Products formed 50 No. Clay Benzene :1 Si Toluene 5:1 323:

benzene 35% ra es i 2 31 51 3 13% 2:3 6. 55 55 Percent Volume Per centPercent Percent Per cent Percent Per cent None None 3.6 (1.0 (x) 29.049.1 1L8 5% (xx).

15 None a2 (7.8) (x) 24.6 41.0 as Very small. None 5.4 4.3 23.6 47.022.1 None.

15 2 4.0 5.0 42.0 2&0 16.8 Do.

3o 2 2.3 7.8 59.9 22.8 22.0 Do. 60

pletely dealkylatedto benzene even at the tem- The above table clearlyshows the remarkably peratures of our process. improved results obtainedin Experiments 4 and In order to more clearly illustrate the inven- 5 byour process of operation. In Experiment 4 tion and to contrast theimproved results ob-' of the above table giving a yield of 42% of the 65tained thereby over the results obtained by prior desired compounds, therecovery of benzene was cracking processes, the following experimentsare practicallycomplete and in Experiment 5 (with cited wherein twoportions of alkyl aromatic a yield of 60% 'of the desired alkyl aromaticcompounds falling in the range of 150 to 250 C. compounds) aconsiderable amount of benzene boiling point and of specificgravity0.865 were was consumed resulting in a corresponding indealkylated. Oneportion of the alkyl aromatic crease in theyield of alkyl benzenes. Inorder compounds was dealkylated by a usual cracking to show that underthe dealkylating action of process and the other portion of the alkylarc-- clay-and the temperatures of our process, alkyl matic compoundswas treated with two. volumes benzenes may be completelydealkylated tobenof benzene and 30% of activated clay, (based on 75 kylated at lowtemperature, the following reaction takes place:

the combined weight of benzene and alkyl aromatics) and dealkylatedaccording to our process. The pressure used in the cracking process was900 lbs/sq. in. and in our dealkylation process zene, a furtherexperiment of dealkylatlon 0t alkyl benzenes was carried out under thesame conditions as in Experiment 4 of the above table but with a longertime of reaction, all other conditions being identical. The followingresults were obtained:

zene to 1 volume of alkyl aromatics in contact with an activated claydealkylation catalyst at a temperature between about 800 F. and about900 F. and under a pressure between about 1000 and about 2500 lbs. persquare inch, heating said mix- 5 Dest uctive dealkylation of highboiling aromatics at 900 F., 15% clay, 2 volumes of benzene per 1 volumeof aromatics Products formed Recovery Time Alkyl No. of Recyclingbenzene Light figfil 5133;, stock Residends mum 0 0 150-210 uum I O. 0.ll

Percent Percent Percent Percent Percent Percent 4 40 99 4. 0 5. 6 42 028. 0 l6. 8 6 58 104 10.4 4.6 36.2 24.3 18.3

From this last table it is seen that with a longer period of reaction104% of benzene is recovered.

We claim:

1. The process of producing relatively low molecular weight alkylaromatic compounds from alkyl aromatic compounds of higher molecularweight which comprises continuously passing a mixture of benzene andsaid higher molecular weight alkyl aromatic compounds in the ratio of A2to 2 volumes of benzene to 1 volume of alkyl aromatics through a heatingzone in contact with an activated clay dealkylation catalyst at atemperature between about 800 F. and about 1050 F. and undersubstantially atmospheric pressure, said mixture being kept in saidheating zone for a sufiioient length of time to produce the desiredalkyl aromatic compounds, withdrawing the treated mixture, separatingthe desired low molecular weight alkyl aromatic compounds and re- 0covering at least substantially all the admixed benzene.

2. The process of producing alkyl aromatic compounds boiling within thegasoline boiling range from alkyl aromatic compounds of higher boilingrange which comprises continuously passing a mixture of benzene and saidhigher boiling alkyl aromatic compounds through a heating zone incontact with an activated clay dealkylation catalyst at a temperaturebetween about 800 F. and about 1050 F. and under substantially atvmospheric pressure, said mixture being kept in said heating zone for asufiicient length of time to produce the desired alkyl aromaticcompounds.

3. The process of producing relatively low molecular weight allgvlaromatic compounds from alkyl aromatic compounds of higher molecularweight which comprises continuously passing a. mixture of benzene andsaid higher molecular weight alkyl aromatic compounds through a'heatingzone containing a dealkylation catalyst comprising an association ofsilicon oxide and aluminum oxide and maintained at a temperature betweenabout 800 F. and about 1050 F. and under substantially atmosphericpressure, said mixture being kept in said heating zone for a sufli'cientlength of time to produce the desired alkyl aromatic compounds,withdrawing treated mixture andrecovering at least substantially all thebenzene admixed therewith.

7o 4. The process of producing alkyl aromatic compounds boiling withinthe gasoline boiling range from alkyl aromatic compounds of higherboiling range which comprises heating a batch mixture of benzene andsaid higher boiling alkyl aromatics in the ratio of to 2 volumes ofbenture for a suflicient length of time to produce the desired alkylaromatic compounds, separating alkyl aromatic compounds of gasolineboiling range from the treated mixture and recovering at leastsubstantially the total quantity of ad- 25 mixed benzene.

5. The process of producing alkyl aromatic compounds boiling within thegasoline bolling range from alkyl aromatic compounds of higher boilingrange which comprises heating a a batch mixture of benzene and saidhigher boiling alkyl aromatic compounds in the presence of an activatedclay dealkylation catalyst at a temperature between about 800 F. andabout 900 F. and under a pressurebetween about 1000 and about 2500 lbs.per square inch, said mixture being heated for a suificient length oftime to produce the desired alkyl aromatic compounds.

6. The process of producing alkyl aromatic compounds boiling in thegasoline boiling range 40 from alkyl aromatic compounds of higherboiling range which comprises treating said latter alkyl aromaticcompounds with benzene at a temperature between about 800 F. and about1050 tion catalyst.

'7. The process of producing aromatic compounds of relatively lowmolecular weight from alkyl aromatic compounds of higher molecularweight which comprises reacting a mixture of 60 said alkyl aromaticcompounds and benzene in the presence of a dealkylation catalystcomprising an association of silicon o :ide and aluminum oxide at atemperature between about 800 F. and about 900 F. and a pressure betweenabout 1000 ll lbs/sq. in. and about 2500 lbs/sq. in.

8. The process of producing aromatic compounds of relatively lowmolecular weight from alkyl aromatic compounds of higher molecularweight which comprises treating said alkyl aro- 00 matic compounds withbenzene at temperatures between-about 800 F. and about 1050 F. in thepresence of a dealkylation catalyst comprising an association of siliconoxide and aluminum oxide.

9. The process of producing relatively low mo- 65 lecular weightaromatic compounds from alkyl cyclic compounds of higher molecularweight which comprises treating said alkyl cyclic compounds with benzeneat a temperature between about 800 F. and about 1050 F. in the presence10 of a dealkylation catalyst comprising an association of silicon oxideand aluminum oxide.

10. In a process for producing alkyl aromatic compounds boiling in thegasoline boiling range from alkyl cyclic compounds of higher boilingtable, the improvement which comprisestre 8 said higher boiling alkylcyclic compounds with benzenein the presence of an activated claydealkylation catalyst and at a temperature between 5 about 800 F. andabout 1050 F. 11. In a process for producing aromatic compounds ofrelatively low molecular weight 'from alkyl cyclic compounds or highermolecular weight, the improvement which comprises treat- 10 ing saidhigher molecular weight alkyl cyclic compounds with benzene in thepresence of a dealkylation catalyst comprising an association of siliconoxide and aluminum oxide and at a temperature between about 800 F. andabout 1050 15 F., and recovering at least substantially all the benzeneused to treat said alkyl cyclic compounds.

- 12. The process of producing aromatic compounds of relatively low'molecular weight from alkyl cyclic compounds of higher molecular.

20 weight which comprises treating said alkyl cyclic compounds with asulmtantially unsaturated aromatic compound containing not more than tworings of relatively low molecular weight at a temperature between about800 F. and about 1050 F. in the presence or a dealkylation catalyst com-5 prising an association of silicon oxide and aluminum oxide.

13. The process of dealkylating alkyl cyclic compounds which comprisestreating said alkyl cyclic compounds with benzene at temperatures 10between about 800 F. and about 1050 F. in the presence of a claydealkylation catalyst.

14. The process of dealkylating alkyl aromatic compounds which comprisestreating said alkyl aromatic compounds with benzene at temperalb turesbetween about'800" F. and about 1050 F. in the presence of a claydealkylation catalyst.

ALEXANDER N. SACHANEN. ROWLAND C. HANSFORD. 20

